Climatic Feedbacks and Desertification: the Mediterranean Model

Meso-meteorological information obtained in several research projects in southern Europe has been used to analyze perceived changes in the western Mediterranean summer storm regime. A procedure was developed to disaggregate daily precipitation data into three main components: frontal, summer storms and Mediterranean cyclogenesis, and working hypotheses were derived on the likely processes involved. The results indicate that the precipitation regime in this Mediterranean region is very sensitive to variations in surface air mass temperature and moisture. Land use perturbations accumulated over historical time, and greatly accelerated in the last 30 years, may have induced changes from an open, monsoon-type regime with frequent summer storms over the mountains inland, to one dominated by closed vertical recirculations where feedback mechanisms favor the loss of storms over the coastal mountains and additional heating of the sea surface temperature during summer. This, in turn, favors Mediterranean cyclogenesis and torrential rains in autumn-winter. Because these intense rains and floods can occur anywhere in the basin, perturbations to the hydrological cycle in any part of the basin can propagate to the whole basin and adjacent regions. Furthermore, present levels of air pollutants can produce greenhouse heating, amplifying the perturbations and pushing the system over critical threshold levels. The questions raised are relevant for the new EU water policies in Southern Europe, and for other regions dominated by monsoon-type weather systems.

MILLAN M.M.;  ESTELA M.J.;  SANZ M.J.;  SEUFERT Guenther; 

2006-02-14

BLACKWELL PUBL LTD

JRC32510

https://publications.jrc.ec.europa.eu/repository/handle/JRC32510,